Manufacture of sized papers



Patented Sept. 29, 1936 UNITED STATES PATENT OFFICE MANUFACTURE or srznn PAPERS Charles R. Outterson, Water-town, N. Y., assignor I to Bennett, Incorporated, East Cambridge,- Mass., a corporation of Massachusetts No Drawing.

Application December 30, 1933, I Serial No. 704,752 1 3 Claims. (01. 92-21) This invention relates to the manufacture of sized papers by a process according to which aqueous sizing compositions consisting essentially of stabilized aqueous dispersions-or emul- 5 sions of unsaponified water-repellent materials are addedto paper-making stock in the beater engine and the materials precipitated on the.

I persed therein; and aqueous dispersions of paraflinwax or other substantially inert hydrocarbon wax or bituminous material stabilized by a soap other than rosin soap, for instance, the saponified portion of Montan wax.

Aqueous dispersions of the foregoing kind can be prepared with their dispersed content of unsaponified water-repellent material in a micro- 25 scopically fine state of sub-division or dispersion.

Such fine particle size is of fundamental importance, as it means that the dispersed waterrepellent material can be disseminated with substantial uniformity through the paper-making 30 stock in the beater engine and then fixed on the fibers through the action of a precipitant in such a way as to have practically'no tendency to separate out during the paper-making operation. Again, the free or unsaponified condition of the 35 dispersed water-repellent material makes for a higher sizing or water-repelling value in the resulting paper with agiven usage of sizing material. Thus the use of aqueous rosin soap or size compositions containing a substantial 40 amount of rosin in free or unsaponified condition dispersed therein leads to a better sized paper and one possessing more snap" and rattle than that realized from the same rosin usage in completely saponified condition. 45 Unfortunately, however, there are instances when excellent aqueous dispersions of the foreing or water-repelling value, but worse than this, coarse particles of water-repellent material are shed onto and accumulate on the various parts of the paper-making machine, including the web-forming wire cloth, the suction boxes and 5 suction rolls, the transfer felt and the press rolls, and even the drier felt, drier drums, and the calender rolls. In fact, this latter problem may 'be so serious as to necessitate a stoppage of the paper-making machine and a cleaning of some of its parts at as short intervals as' every hour.

There are various instances when a stabilized, aqueous dispersion of unsaponified water-repellent material may undergo coagulation or undesirable fiocculation upon being added to papermaking stock in the beater engine and hence give rise to the foregoing troubles, but in all in-. stances, the underlying causeis the presence in the beater water, that is, the water serving as the slushing medium for the stock, of electrolytes in sufiicient amount to destroy the stabilizenassociated with the dispersion and, accordingly, to coagulate or flocculate the dispersed particles before they have been or can be distributed uniformly throughout the stock. Thus, bleached pulps may give trouble when they are notior cannot, in practice be washed completely free of bleach or the reaction products of the bleaching operation, as the calcium salts or other chemical residues from the bleaching operation are destructive of the stabilizing agent in the dispersion. The same is true of residual acid, calcium bisulphite, or other calcium salts that may be associated with commercial unbleached sulphite pulps. So, too, difliculty may come from the use of hard waters containing calcium or magnesium salts in slushing the stock in the beater engine or from a similar use of white water recovered from the paper-making machine and containing coagulant, filler, pigment, etc. In fact, two or more of the foregoing undesir able conditions may. prevail at once. i In' accordance with the present invention, I peptize the water associated with the papermaking stock in the beater engine with substan of substantially completely saponified rosin, that is, sodium resinate, for this purpose is distinctly advantageous in that first, it is highly eifective in removing from the sphere of potential reaction and precipitating as calcium resinate the calcium ion, which is in many cases the source of trouble, without yielding other troublesome electrolytes as may be true when the usual watersoftening agents are employed; second, it may be used in excess to ensure the desired peptizing action and then be precipitated by alum or other suitable precipitant as an effective sizing agent; and, third, it is a comparatively inexpensive agent that is likely to be present or that can be prepared without difliculty in a paper mill. I wish to emphasize the necessity of using substantially completely saponified rosin as the peptizing agent, for should a noteworthy amount of dispersed free rosin be added to a troublesome paper-making stock along with rosin soap, it would be coagulated or flocculated and cause a nuisance on the paper-making machine, as already observed. Once the water component of the stock has been appropriately peptized with substantially completely saponified rosin, the stock may be sized to advantage with an aqueous solution of rosin soap containing a substantial amount of rosin in free or unsaponifled condition dispersed therein, with an aqueous dispersion of paraflin wax stabilized with rosin soap, or with any of the other stabilized aqueous dispersions or emulsion of unsaponified water-repellent materials hereinbefore mentioned, for instance, a dispersion of paraflin wax or other inert hydrocarbon wax or bituminous material stabilized by the saponified portion of Montan wax.

It is a comparatively easy matter to determine how my invention should be applied to a given paper-making stock which is troublesome when a stabilized aqueous dispersion of unsaponified water-repellent material is added directly thereto. Thus, I take a sample of the water-slushed stock and quantitatively determine how much of the completely saponified rosin is required to peptize the water with reference to the particular stabilized dispersion of water-repellent material that is to be used in sizing the stock. Or I can introduce into the water-slushed stock, say, about 1% of completely saponified rosin, based on the dry weight of the stock, and, after it has been thoroughly mixed with the stock, withdraw a sample of the water from the stock and add thereto a little of the dispersion to be used as a. sizing material so as to determine whether the water associated with the stock contains enough of the saponified rosin to have become peptized thereby. If such is not the case, I can add more completely saponified rosin to the water-slushed stock until I arrive at the point where I can safely introduce thereinto the dispersion to be used as a sizing material. The point at which the stock can be safely treated with the dispersion to be used as a sizing material is that at which the water component of the stock does not generate microscopically coarse particles upon treatment with such dispersion.

A typical specific instance when the principles of my invention were applied to good advantage was in'the manufacture of high grade wall paper from a beater furnish consisting partly of bleached sulphite pulp and partly of de-inked and bleached old paper stock. The de-inked and bleached old paper stock had a comparatively short fibrous structure which could not in practice be readily washed clean of bleach and hence contained enough residual bleach to exert-a desiderable trouble.

clded coagulating eifect upon a rosin size of high dispersed free rosin content and upon a stabilized aqueous dispersion of paraffin wax. In such case, I added to the beater furnished with the bleached sulphite pulp and the de-inked and bleached old paper stock about 1% of completely saponified rosin, based on the dry weight of the stock mixture, ran the beater engine to effect a substantially uniform dissemination of the completely saponified rosin throughout the water component of the stock, and then added an aqueous dispersion of paraifin wax in an aqueous rosin soap solution in the amount of about 1% total solids content, based on the dry weight of the stock. The solids content of the dispersion consisted of about 38% of the parafiin wax and about 62% of the rosin, some of the rosin being in a free or unsaponified condition. After thedispersion had been uniformly incorporated throughout the stock by the operation of the engine, alum was added as ordinarily in suflicient amount to fix the dispersed particles to the stock and the stpck run ofi on a paper-making machine. No trouble was encoun tered on the paper-making machine as a result of the particular sizing materials employed; and the sizing or water-repelling value of the sizing materials was realized to the fullest extent uniformly throughout the finished paper.

Another typical specific instance when the principles of my invention were applied to good advantage was in the manufacture of a rosinsized wrapping paper from only unbleached sulphite pulp as the paper-making stock. In such case, the use of rosin size of high free rosin content in the usual manner had given rise to con- The fact was that because of the presence in the unbleached sulphite pulp of residual acids and other electrolytes, the addition directly to such pulp in the beater engine of a rosin size composition of high free rosin content occasioned the coagulation of the free rosin and the accumulation of rosin on the Fourdrinier wire and the other parts of the Fourdrinier paper-making machine, causing serious difliculty in the operation of the machine and giving rise to an improperly sized paper. The procedure accordant with the present invention in such case was to introduce into the water-slushed, unbleached sulphite pulp in the beater engine about 1% of completely saponified rosin, based on the dry weight of the stock, mix the ingredients thoroughly, and then add to the stock about 2% rosin size solids, based on the dry weight of the stock, in the form of an aqueous rosin size composition containing about 45% free rosin, the rest of the rosin being in the form of sodium resinate. After the rosin size was thoroughly commingled with the stock, alum was used as a precipitant as ordinarily to fix the free rosin and the rosin soap to the stock, and the stock run ofi on a paper-making machine. The resulting paper was thus sized with rosin size, 30% of which was in free condition. It was'characterized by high water repellency and good snap and rattle by virtue of its free rosin content. If it were attempted to introduce all of the sizing materials at once into the stock in the form of an aqueous sizing composition containing 30% free rosin, serious trouble would ensue on account of coagulation of virtually all of the free rosin. On the other hand, if all of the rosin were used in a completely saponified condition, the desired high sizing value and other qualities sought in the paper would not be attained even though papermaking machine difliculties would be obviated.

My invention extends to other situations wherein difiiculty is encountered in the sizing of water-slushed paper-making stock on account 01' the tendency of such stock to destroy the stability of stabilized aqueous dispersions or emul- 4 sioris of unsaponified water-repellent materials added thereto for sizing purposes, the foregoing examples being illustrative only. When I saythat the water component of the water-slushed stock is peptized with substantially completely saponified rosin, I mean that whereas the water component may initially be so charged with electrolytes as to flocculate or coagulate stabilized aqueous dispersions of unsaponified water-repellent materials hereinbefore mentioned added for sizing-purposes to the stock, no such tendency exists in the stock whose water component has been treated with the completely saponified rosin which may, in fact, be used in excess so as to prises first adding to the papermaking stock rosin soap in amount sumcient to peptize the water component of the stock, then adding to the stock a rosin-soap-stabilized aqueous dispersion of unsaponified waterproofing material, said unsaponified waterproofing material including free rosin, precipitating ,the rosin soap and unsaponified waterproofing material, and running the stock oil? on a papermaking machine.

' 2. A method of making sized paper which comprises first adding to thepapermaking stock rosin soap in amount suflicient to peptize the water component of the stock, then adding to the stock an aqueous rosin sizing composition, a substantial proportion of whose rosin content is free and the rest of whose rosin content is rosin soap, adding alum to precipitate the resin soap and free rosin, and running the stock off on a papermaking machine.

3. A method of making sized paper which comprises first adding to the papermaking stock rosin soap in amount sufficient to peptize the water component of the stock, then adding to the stock a rosin-soap-stabilized aqueous dispersion of wax and free rosin, adding alum to precipitate the rosin soap, wax, and free rosin, and running the stock off on a papermaking machine:

cHARLEs R. OUTTERSON. 

